The remainder() function returns the remainder of the two arrays, element-wise. 0 is returned if the second number is 0:

a = np.arange(-4, 4)
print("Remainder", np.remainder(a, 2))

The result of the remainder() function is shown as follows:

Remainder [0 1 0 1 0 1 0 1]

The mod() function does exactly the same as the remainder() function:

print("Mod", np.mod(a, 2))

The result of the mod() function is shown as follows:

Mod [0 1 0 1 0 1 0 1]

The % operator is just shorthand for the remainder() function:

print("% operator", a % 2)

The result of the % operator is shown as follows:

% operator [0 1 0 1 0 1 0 1]

The fmod() function handles negative numbers differently than mod(), fmod(), and % do. The sign of the remainder is the sign of the dividend, and the sign of the divisor has no influence on the results:

print("Fmod", np.fmod(a, 2))

The fmod() result is printed as follows:

Fmod [ 0 -1  0 -1  0  1  0  1]